MITIGATION OF POWER QUALITY DISTURBANCES IN WIND TURBINE INTEGRATED POWER GRID BY STATCOM

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1 MITIGATION OF POWER QUALITY DISTURBANCES IN WIND TURBINE INTEGRATED POWER GRID BY STATCOM P. Yedukndlu, M. Bl Subbreddy, Meer Shreef Shik M. Teh Shlr (P.E), Deprtment f EEE, Prksm Engineering Cllege, Kndukur, Andhr Prdesh, Indi, kndlu.pkl@gmil.m Prfessr & H.O.D, Deprtment f EEE, Prksm Engineering Cllege, Kndukur, Andhr Prdesh, Indi, blsubbreddy@yh.m Assistnt Prfessr, Deprtment f EEE, Prksm Engineering Cllege, Kndukur, Andhr Prdesh, Indi, meershriefsheik@gmil.m Abstrt A pwer ulity disturbne is defined s nnstndrd vltge, urrent r freueny tht results in dmge f end user euipments. Utility distributin netwrks, sensitive industril lds nd ritil mmeril pertins suffer frm vrius types f utges nd servie interruptins whih n st signifint fin nil lsses. The funtining f the wind turbine nd there by pwer ulity re mesured n the bsis nd the nrms fllwed rding t the guideline speified in Interntinl Eletr tehnil Cmmissin stndrd, IEC The influene f the wind turbine in the grid system nerning the pwer ulity mesurements re the tive pwer, vritin f vltge, fliker, hrmnis, nd eletril behvir f swithing pertin nd these re mesured rding t ntinl/interntinl guidelines. The develpment f pwer eletrnis devies suh s Flexible AC Trnsmissin Systems(FACTS) nd Custms pwer devies re emerging brnh f tehnlgy prviding the pwer system with verstile new ntrl pbilities. The pper study demnstrtes the pwer ulity prblem due t instlltin f wind turbine with grid. In this prpsed sheme STATIC COMPENSATOR (STATCOM) is nneted t pint f mmn upling with bttery energy strge system (BESS) t mitigte the pwer ulity issues. The bttery energy strge is integrted t sustin the rel pwer sure under flututing wind pwer. The STATCOM ntrl sheme fr the grid nneted wind energy genertin system fr pwer ulity imprvement is simulted using MATLAB/SIMULINK in pwer system bl k set. Finlly the prpsed sheme is pplied fr blned nn liner lds t study perfrmne f STATCOM in mitigting the pwer ulity prblems tht rise due t internnetin f wind sttin t pwer grid. Als the simultin study is extended t study the perfrmne f STATCOM with BESS during the fult stte with mesurement f tive pwer, retive pwer, pwer ftr nd THD redutin. Key Wrds Sttm, BESS, bngbng urrent ntrller, PCC. INTRODUCTION One f the min prblems in wind energy genertin is the nnetin t the grid. Injetin f wind pwer int the grid ffets the pwer ulity resulting in pr perfrmne f the system. The wind energy system fes freuently flututing vltge due t the nture f wind nd intrdutin f hrmnis int the system. Injetin f the wind pwer int n eletri grid ffets the pwer ulity. While fssil fuels will be the min fuels fr therml pwer, there is fer tht they will get exhusted eventully in the next entury. T hve sustinble grwth nd sil prgress, it is neessry t meet the energy need by utilizing the renewble energy resures like wind, bimss, hydr, genertin et. In sustinble energy system, energy nservtin nd the use f renewble sure re the key prdigm. The need t integrte the renewble energy like wind energy int pwer system is t minimize the envirnmentl impt n nventinl plnt. With the help f speil lletrs, we n pture prt f this energy nd put it t use fr ur eletril pwer supply needs. As lng s sunlight, wter nd wind ntinue t flw nd trees nd ther plnts ntinue t grw, we hve ess t IJESAT AugSep 0 40

2 b A B C redy f supply f energy. In this prpsed sheme Stti Cmpenstr (STATCOM) is nneted t pint f mmn upling with bttery energy strge system (BESS) t mitigte the pwer ulity issues. The bttery energy strge is integrted t sustin the rel pwer sure under flututing wind pwer. The STATCOM ntrl sheme fr the grid nneted wind energy genertin system fr pwer ulity imprvement is simulted using MATLAB/SIMULINK in pwer system blk set. The effetiveness f the prpsed sheme relieves the min supply sure frm the retive pwer demnd f the ld nd the indutin genertr. It is ls hving pbility f hrmni elimintin nd ld blning. The prpsed STATCOM ntrl sheme fr grid nneted wind energy genertin fr pwer ulity imprvement hs fllwing bjetives. ) Unity pwer ftr t the sure side s well s Retive pwer supprt frm STATCOM t wind genertr nd ld. ) Simple bngbng ntrller fr STATCOM t hieve fst dynmi respnse. ) Redutin in THD in sure urrent whih mkes ther ld n line t be sfe.. PROPOSED CONCEPT FOR POWER QUALITY In this nfigurtin, wind genertins re bsed n nstnt speed tplgies with pith ntrl turbine. The indutin genertr is used in the prpsed sheme beuse f its simpliity, it des nt reuire seprte field iruit, it n ept nstnt nd vrible lds, nd hs nturl prtetin ginst shrt iruit. The vilble pwer f wind energy system is presented s belw. P wind A wind In this nfigurtin, wind genertins re bsed n nstnt speed tplgies with pith ntrl turbine. The indutin genertr is used in the prpsed sheme beuse f its simpliity, it des nt reuire seprte field iruit, it n ept nstnt nd vrible lds, nd hs nturl prtetin ginst shrt iruit. The vilble pwer f wind energy system is presented s belw. v Spe L L L Mesuremntes A Bb C I ThreePhse Breker v Spe L5 L L4 0 Cnstnt Disrete, Ts = 5e006 s A Bb C I pwergui Genertr speed (pu) Pith ngle (deg) Wind speed (m /s) g A B C Wind Turbine Universl Bridge A Bb C I Tm (pu) Cd DC ltge Sure v A B C A bb C I Nnliner ld [d] Gt d Gt Spe L6 Tm A B C Cntrl Cikuit m indutin genertr Fig..: Simulink Mdel f DSTATCOM Pwer Ciruit with BESS fr Pwer Qulity Imprvement Where ρ (kg/m ) is the ir density nd A (m ) is the re swept ut by turbine blde, is the wind speed in mtr/s. The munt f ir pssing thrugh n re A, with velity, is A, nd its mss m is eul t the prdut f vlume nd density ρ f ir, then m ra Substituting this vlue f mss in the kineti energy eutin, Kineti Energy A A This eutin tells us tht s the energy is diretly prprtinl t ube f wind speed, smll inrese in wind speed n hve mrked effet n the pwer f the wind. It is nt pssible t extrt ll kineti energy f wind, thus it extrt frtin f pwer in wind, lled pwer effiient Cp f the wind turbine, nd is given in eutin belw. P C meh p P wind where Cp is the pwer effiient, depends n type nd perting nditin f wind turbine.. BESSSTATCOM The bttery energy strge system (BESS) is used s n energy strge element fr the purpse f vltge regultin. The BESS will nturlly mintin d pitr vltge nstnt nd is best suited in STATCOM sine it rpidly injets r bsrbed retive pwer t stbilize the grid system. It ls ntrl the distributin nd trnsmissin system in very fst rte. When pwer flututin urs in the system, the BESS n be used t level the pwer flututin by hrging nd dishrging pertin. The bttery is nneted Gte IJESAT AugSep 0 4

3 in prllel t the d pitr f STATCOM. The STATCOM is threephse vltge sure inverter hving the pitne n its DC link nd nneted t the pint f mmn upling. The STATCOM injets mpensting urrent f vrible mgnitude nd freueny mpnent t the bus f mmn upling.. SYSTEM OPERATION The shunt nneted STATCOM with bttery energy strge is nneted with the interfe f the indutin genertr nd nnliner ld t the PCC in the grid system. The STATCOM mpenstr utput is vried rding t the ntrlled strtegy, s s t mintin the pwer ulity nrms in the grid system. The urrent ntrl strtegy is inluded in the ntrl sheme tht defines the funtinl pertin f the STATCOM in the pwer system. A single STATCOM using insulted gte biplr trnsistr is prpsed t hve retive pwer supprt, t the indutin genertr nd t the nnliner ld in the grid system. The min blk digrm f the system pertinl sheme is shwn in Fig... A STATCOM nsists f twlevel ltge Sure Cnverter (SC), DC energy strge devie, upling trnsfrmer nneted in shunt t the distributin netwrk thrugh upling trnsfrmer. The SC nverts the DC vltge rss the strge devie int set f threephse AC utput vltges. These vltges re in phse nd upled with the AC system thrugh the retne f the upling trnsfrmer. Suitble djustment f the phse nd mgnitude f the STATCOM utput vltges llws effetive ntrl f tive nd retive pwer exhnges between the STATCOM nd the AC system. Suh nfigurtin llws the devie t bsrb r generte ntrllble tive nd retive pwer. A singlephse euivlent iruit f STATCOM is shwn in Fig.. Where, R is inluded t represent smll lsses in the swithing devies f SC. R s nd L represent the euivlent iruit f the tietrnsfrmer between system vltges U s nd the utput vltge U I f STATCOM. Fig..: Singlephse euivlent iruit f STATCOM Fig..: Grid nneted System fr Pwer Qulity Imprvement. MODELING OF STATCOM It is ssumed tht the sure is blne, sinusidl threephse vltge supply with the freueny ω. Sine retive pwer mpenstin is desired, it is nvenient fr this nlysis t tke the ngle f the input the referene ngle. Hwever the system is designed bsed n fllwing ssumptins. The U s, U, U s re defined s instntneus vlues f system phse vltge nd n be given by: U U U s s U s sin wt sin wt sin wt Where, U s is rms vlue f system phse vltge. The utput vltges f DSTATCOM, u j, u ib nd u i n be given by: The three AC mins vltges re blned The three phse ld is blned nd liner The inverter swithes re idel DC link utput is ripple free The filter mpnents re retive nd liner IJESAT AugSep 0 4

4 i urrent ( ) re subtrted s s t tivte the pertin f STATCOM in urrent ntrl mde. The ntrl system sheme fr generting the swithing signls t the STATCOM is shwn in Fig4.. Fig.: etr digrm f STATCOM () Cpitive mde, (b) Indutive mde, () Ative pwer relese nd (d) Ative pwer bsrptin u u i u i K t mu d sin wt K t mu d sin wt K t mu d sin wt Fig.4.: System pertin with ntrl sheme Where, KT is turn s rti f the tietrnsfrmer, m is the mplitude mdultin rti f SC utput vltge; its vlue depends n the type f SC. U DC is the DClink pitr s vltge f SC nd is the phse ngle differene between vltge u s nd urrent Is. 4. CONTROL SCHEME The ntrl sheme pprh is bsed n injeting the urrents int the grid using bngbng ntrller. The ntrller uses hysteresis urrent ntrlled tehniue. Using suh tehniue, the ntrller keeps the ntrl system vrible between bundries f hysteresis re nd gives rret swithing signls fr STATCOM pertin. The ntrl lgrithm needs the mesurements f severl vribles suh s threephse sure urrent( i ), DC vltge ( v d), inverter urrent ( i ib ) with the help f sensr. The urrent ntrl blk, reeives n input f referene urrent ( i * ) nd tul Fig.4.: Cntrl Sheme 4. GRID SYNCHRONIZATION In threephse blne system, the RMS vltge sure mplitude is lulted t the smpling freueny frm the sure phse vltge (s,, s) nd is expressed, s smple templte s m, smpled pek vltge, s in eutin belw sm s s The inphse unit vetrs re btined frm AC sure phse vltge nd the RMS vlue f unit vetr s shwn in eutin belw IJESAT AugSep 0 4

5 u s s sm, u sm, u s s sm. The inphse generted referene urrents re derived using inphse unit vltge templte s in eutin belw i I u, i I u I u S S Sb Sb S s where I is prprtinl t mgnitude f filtered sure vltge fr respetive phses. This ensures tht the sure urrent is ntrlled t be sinusidl. The unit vetrs implement the imprtnt funtin in the grid nnetin fr the synhrniztin fr STATCOM. S.N Prmeters Rting Grid ltge Phse,45, 50HZ. Indutin Mhine, i.5ka,45,50hz,p=4, L 0., L 0. 9 S r. Line series indutne 4. Inverter prmeters 0.05mH DC link ltge:800dc Link Cpitne:00µF Swithing Freueny:KHZ 5. IGBT Rtings Clletr ltge:00 Frwrd Current:50A Pwer Disiptin:00Wtts Tble 4.: System Prmeters 4. DQTRANSFORMATION THEORY FOR REFERENCE FOR CURRENT GENERATION There re severl methds t extrt the hrmni mpnents frm the deteted threephse wvefrms. Amng them, the slled p thery bsed n time dmin hs been widely pplied t the hrmni extrtin iruit f tive filters. The deteted threephse vltge is trnsfrmed int the D Q rdintes. Tw send rder digitl high pss filters (HPFs) with the sme ut ff freueny s 7Hz extrt the d mpnent hd *, h * nd 0 whih rrespnds t the fundmentl freueny in the rdintes. Fig.4. Blk digrm f the ntrl iruit euipped with the funtin f vltge regultin nd hrmni dmping. I I I d s Kghhd d d d s s b K gh h 4. ABCDQ0 TRANSFORMATION This blk perfrms the b d0 trnsfrmtin n set f three phse signls. It mputes the diret xis d, udrti xis, zer seuene untities, in tw xis rtting referene frme rding t fllwing trnsfrmtin. d sin s b wt sin wt sinwt wt s wt swt b b 4.4 DQ0ABC TRANSFORMATION It trnsfrms three untities (diret xis, udrti xis nd zer seuene mpnents) frm three phse untities expressed in tw xis referene frme bk t referene phse untities. IJESAT AugSep 0 44

The fllwing trnsfrmtin is used: b d d d sin wt swt sin wt sin wt s wt s wt The btined urrent referene is nverted three phse urrent referene by inverse D Q trnsfrmtin I *, I * b, nd I *.

The btined referene urrent is given t PI ntrller in rder t generte ntrlled gte signl fr DSTATCOM.

6 The fllwing trnsfrmtin is used: b d d d sin wt swt sin wt sin wt s wt s wt The btined urrent referene is nverted three phse urrent referene by inverse D Q trnsfrmtin I *, I * b, nd I *. The threethree phse referene mpensting urrent is mpred with the STATCOM mpensting urrent extrted frm system. Thus three phse mpensting urrent I, I b, nd I re prdued. The btined referene urrent is given t PI ntrller in rder t generte ntrlled gte signl fr DSTATCOM. CASE I: BALANCED NON LINEAR LOAD WITH BATTERY CONNECTED DSTATCOM: The pwer funtin f STATCOM nneted t PCC fr pwer ftr rretin system is with BESS is simulted using MAT LAB Simulink blk withut fult. The trnsient respnses f distributin system with APC fr supply vltges ( v ) supply urrents ( i ), ld urrents ( i lb, ilb ndi l ), APC urrents ( i, i b, i ) re shwn belw. 4.5 BANGBANG CURRENT CONTROLLER The referene urrent is generted nd tul urrent re deteted by urrent sensrs nd re subtrted fr btining urrent errr fr hysteresis bsed bngbng ntrller. Thus the ON/OFF swithing signls fr IGBT f STATCOM re derived frm hysteresis ntrller. The swithing funtin S A fr phse is expressed s in eutin belw. When Is < (I*s HB), SA = 0 nd when Is > (I* HB), SA = Where HB is hysteresis urrentbnd, similrly the swithing funtin SB, SC n be derived fr phses b nd respetively. 5. SYSTEM PERFORMANCE The STATCOM ntrl sheme fr the grid nneted wind energy genertin system fr pwer ulity imprvement is simulted using MATLAB/SIMULINK in pwer system blk set. Finlly the prpsed sheme is pplied fr blned nn liner lds t study perfrmne f STATCOM in mitigting the pwer ulity prblems tht rise due t internnetin f wind sttin t pwer grid. Als the simultin study is extended t study the perfrmne f STATCOM with BESS during the fult stte with mesurement f tive pwer, retive pwer, pwer ftr nd THD redutin. Fig.6.: Simultin results fr Blned Nn Liner Ld with bttery nnetin () Sure urrent. (b) Ld urrent. () Inverter injeted urrent. (d) ltge Frm fig 6. it is evident tht when STATCOM is n, sure urrent THD is redue s well s the pwer ftr is rreted. Here mpenstr is turned n t 0. sends. Fig.6.: Simultin results f pwer ftr fr Nn liner Ld Fig. 6. shws pwer ftr t be pprximtely unity fter the mpenstr n t 0. se. 6. MAT LAB RESULTS Here Simultin results re presented fr Tw ses. In se ne, ld is blned nn liner with DSTATCOM OPERATION with BESS. In se tw, ld is blned nn liner ld with STATCOM pertin BESS n fult. Fig.6.: System Ative Pwer nd retive pwer Mesurement IJESAT AugSep 0 45

Frm fig 6.6 it is evident tht when STATCOM is n sure urrent THD is redue s well s the pwer ftr.

4: Simultin results fr sure urrent THD Frm fig 6.

% withut STATCOM but with sttm it is rund.4%. Fig.6.7: Simultin results f pwer ftr fr Nn liner Ld Fig. 6.

Here fult is reted during 0.05 t 0.5 se. Fig 6.5Simultin results f sure urrent THD with filter Frm fig 6.

CASE II: BALANCED NON LINEAR LOAD WITH BATTERY CONNECTED DSTATCOM WITH FAULT OPERATION: The pwer funtin f STATCOM

The trnsient respnses f distributin system with APC fr supply vltges Fig 6.

8 it is evident tht ttl hrmni distrtin is redued when mpenstr is n frm 0. se. The THD is fund t be.

7 Frm fig 6.6 it is evident tht when STATCOM is n sure urrent THD is redue s well s the pwer ftr. Here mpenstr is turned n t 0. sends. The durtin f fult is 0.05 t 0.5 se. Fig 6.4: Simultin results fr sure urrent THD Frm fig 6.4 it is evident tht ttl hrmni distrtin is redued when mpenstr is n frm 0. se. The THD is fund t be.% withut STATCOM but with sttm it is rund.4%. Fig.6.7: Simultin results f pwer ftr fr Nn liner Ld Fig. 6.7: shws pwer t be unity fter the mpenstr n t 0. se nt nly tht STATCOM effiiently rrets pwer ftr during fults ls. Here fult is reted during 0.05 t 0.5 se. Fig 6.5Simultin results f sure urrent THD with filter Frm fig 6.5 it is evident tht THD n be redued by use f filter. CASE II: BALANCED NON LINEAR LOAD WITH BATTERY CONNECTED DSTATCOM WITH FAULT OPERATION: The pwer funtin f STATCOM nneted t PCC fr pwer ftr rretin system is with BESS is simulted using MAT LAB Simulink blk withut fult. The trnsient respnses f distributin system with APC fr supply vltges Fig 6.8: Simultin results fr sure urrent THD Frm fig 6.8 it is evident tht ttl hrmni distrtin is redued when mpenstr is n frm 0. se. The THD is fund t be.% withut STATCOM but with sttm it is rund.4% during the fult ls. ( v ) supply urrents ( i ), ld urrents ( i lb, ilb ndi l ), APC urrents ( i, i b, i ) re shwn belw. Fig 6.9: Simultin results f sure urrent THD with filter Frm fig 6.9 it is evident tht THD n be redued by use f filter. Fig.6.6: Simultin results fr Blned Nn Liner Ld with bttery nnetin () Sure urrent. (b) Ld urrent. () Inverter injeted urrent. (d) ltge Fig.6.0: System Ative Pwer nd retive pwer Mesurement IJESAT AugSep 0 46

The ltter feture enbles its pplitin fr mpenstin f dips ming frm the supplying netwrk.

8 II CONCLUSION STATCOM system is n effiient men fr mitigtin f PQ disturbnes intrdued t the grid by DERs. STATCOM mpenstr is flexible devie whih n perte in urrent ntrl mde fr mpensting vltge vritin, unblne nd retive pwer nd in vltge ntrl mde s vltge stbilizer. The ltter feture enbles its pplitin fr mpenstin f dips ming frm the supplying netwrk. The simultin results shw tht the perfrmne f STATCOM system hs been fund t be stisftry fr imprving the pwer ulity t the nsumer premises. STATCOM ntrl lgrithm is flexible nd it hs been bserved t be pble f rreting pwer ftr t unity, eliminte hrmnis in supply urrents nd prvide ld blning. It is ls ble t regulte vltge t PCC. The ntrl lgrithm f STATCOM hs n inherent prperty t prvide selfsupprting DC bus f STATCOM. It hs been fund tht the STATCOM system redues THD in the supply urrents fr nnliner lds. Retifierbsed nnliner lds generted hrmnis re eliminted by STATCOM. When singlephse retifier lds re nneted, STATCOM urrents blne these unblned ld urrents. REFERENCES [] Hn. A, Hung. Q, Brn. M, Bhtthry. S nd Litzenberger. W, STATCOM impt study n the integrtin f lrge wind frm int wek lp pwer system, IEEE Trns. Energy Cnv., vl., n., pp. 6, Mr [] Heier. S, Grid Integrtin f Wind Energy Cnversins. Hbken, NJ: W iley, pp , 007. [] Kinj. T nd Senjyu. T, Output leveling f renewble energy by eletri duble lyer pitr pplied fr energy strge system, IEEE Trns. Energy Cnv., vl., n., Mr [4] Mnel. J, Pwer eletrni system fr grid integrtin f renewble energy sure: A survey, IEEE Trns. Ind. Eletrnis, Crrs vl. 5, n. 4, pp , 006. [5] Milnds. M. I, Cdvi. E. R, nd Gnzlez. F. B, Cmprisn f ntrl strtegies fr shunt tive pwer filters in three phse fur wire system, IEEE Trns. Pwer Eletrn., vl., n., pp. 9 6, Jn [6] Mhd. S. W nd Awre. M., Pwer ulity issues & it s mitigtin tehniue in wind energy nversin, in Pr. f IEEE Int. Cnf. Qulity Pwer & Hrmni, Wllngng, Austrli, 008. [7] Snnin. A, Glbl pwer systems fr sustinble develpment, in IEEE Generl Meeting, Denver, CO, Jun [8] Wind Turbine Generting System Prt, Interntinl stndrdiec 6400, 00. BIOGRAPHIES Mr. P. Yedukndlu student f Prksm Engineering Cllege is urrently pursing M.Teh in Pwer Eletrnis speilistin.he mplteted B.Teh (EEE) frm JNTUK. His re f interests inludes Fts, AC & DC Drives. Mr. M.Bl Subb Reddy, HOD(EEE Dept.,) in Prksm Engineering Cllege Pursuing P.hd in JNTUK. He gt M.Teh,POW ER SYSTEMS frm NIT, Trihy. He mpleted B.Teh (EEE) frm Mdrs Uiversity. His res f reserh interest inlude Pwer Eletrnis, Eletril mhines nd AC & DC drives. Mr. SK. Meer Shreef is Asst. Prfessr in EEE Dept., f Prksm Engineering Cllege,kndukur. He mplteted M.Teh,POW ER ELECTRONICS frm JNTUK. He mpleted B.Teh (EEE) frm Ann Uiversity.His re f interests inludes in the subjets f Mhine Mdelling, Fts et., IJESAT AugSep 0 47

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nanox 200 line high-speed piezo translation stages high-speed piez trnsltin stges nn 200 line 240μm rnge f mtin highest dynmil perfrmne exellent guidne ury 0.4 nm reslutin Ø 3mm entrl perture pplitins: mhine tls lser ptis life siene snning systems fig.: